data with type "DATE"~~ QUESTION ABOUT comparing date!!

HI everyone! I have a problem with finding date within a range.In my database, there's a table with a field "updatedate", which is of date type.I want to find out the record with an "updatedate" within a range (typed by user), but i do not know the syntax for comparing date (YYYY-MM-DD). I've tried ">=" and "<=" but in vain.Can anyone help me?? Thanks a lot!!!